I. Field of the Invention
This invention relates, generally, to the field of computer-related peripheral devices used for data entry through directly pointing the devices to a target location on the screen and, relates, more particularly, to an improved apparatus and method therefor which is used to locate the position on the display of a computer or interactive television where the pointer, i.e., pointing device, is aimed at.
II. Description of the Prior Art
Computer-related peripheral devices such as pointers (or input devices) include, for example, keyboards, joysticks, mice, trackballs, light pens, styli, etc. A function of such pointers is to position a cursor at a desired location on the computer display. Once the target position is located by the cursor, the computer can then be instructed to perform an operation such as to perform a menu selection or a function which selects a computer application program or, for that matter, perform icon/menu selection or web-browsing as it relates to interactive television (WEB TV). It is interesting to note, however, that pointing devices such as mice, styli, trackballs, joysticks, etc., have little or nothing in common with natural pointing. In fact, such conventional cursor locating devices are not very convenient to use as a pointer for moving the cursor to a target location. For example, the computer mouse is not convenient in cursor movement noting that the user must move the mouse over the area on a mouse pad or on a flat surface through repeated interruptive movement of the user's arm. As to mobile computing, certain constraints on pointers or input devices that are not present in typical work station environments are present. For example, in laptop computers, pointers or input devices cannot be too large or too expensive and they must be contained within the mobile unit (e.g., laptop) or easily attached to it. The input devices most frequently available with notebook computers such as laptops, for example, trackballs, scratch pads and isometric joysticks, satisfy such constraints but, however, are still used in a relatively difficult manner as indirect pointers which most users, it is believed, find less than fully satisfactory.
Attempts have been made earlier to alleviate the difficulties and problems associated with indirect pointing devices such as those mentioned above. One example is disclosed in Japanese laid-open application publication No. 2-268315, published Nov. 2, 1990. According to the scheme disclosed therein, a cursor is moved to a target position on the computer display by following the coordinate position aimed at a track pad. Although a finger-mounted LED is used as a pointer so as to allow the computer operator to easily set the desired coordinates without releasing his or her hand from the keyboard, such pointing scheme, nonetheless, is still an indirect attempt at setting the coordinates of the target position on the computer display. This is because the finger-mounted pointer is aimed at a position on the secondary plane-shaped light reception part (i.e., a tracking pad), which reception part or tracking pad is arrayed with an infrared (IR) photodetection scheme.
Practically speaking, such an IR responsive pad is used in a manner analogous to a "track pad", to control the relative motion of a cursor on the screen. Such an approach to a pointing device is somewhat clumsy as well as being an indirect pointer. For one, the computer user must aim the finger-mounted LED on the track pad and not on the display and, at the same time, follow the movement of the cursor on the computer display to make sure the cursor moves to the target position. This takes away from the natural benefit one would receive from pointing directly at the display using one's finger as a pointer. Also, employing a separate track pad which is infrared (IR) responsive requires a dense array of sensors and, presumably, must necessarily employ a rather sophisticated control algorithm involving an extra switch used for "clutching" to set the X-Y coordinates of the target position on the screen. The dense array of sensors and the separate track pad also requires an unnecessary expense in addition to a more sophisticated control algorithm.
Many other input device (pointer) schemes have developed over the years. However, such pointers are either functioning as indirect pointers or are associated with a complicated control algorithm in addition to being quite costly to implement. As an example of such prior schemes, U.S. Pat. No. 5,009,501 discloses using a gun as a pointer for an interactive video game (see FIG. 8 of that patent). The emitter of the gun pointer, which emits a field of ultrasonic radiation, is directly pointed to a target on the screen which target is sensed by the ultrasonic receivers around the outer periphery of the TV screen. However, in order to determine the target location on the screen that the gun is aiming at, it is necessary to employ a control algorithm that not only considers the intensities of the detected radiation by the sensors but also the relative angles as well as the range (distance) between the ultrasonic frequency transmitter and the ultrasonic sensors. This patent also discloses schemes in which the signal is a pulsed IR signal. However, in each of the disclosed embodiments in that patent, which employs IR radiation, at least two LED transmitters are employed--one transmitting an IR signal having a wide field of radiation and the second transmitting an IR signal having a narrow field of radiation. In such instances, also, the algorithm that would be required must take into account the distance between the emitter and receiver. In FIG. 9 of that patent, the scheme employed has a directional source comprised of three LEDs which point to three different directions in relation to the screen so as to generate information along two different planes. Such is considered quite cumbersome and would typically involve also the measuring of distance to determine the intensities of the signals received. Such a scheme as that taught in U.S. Pat. No. 5,009,501 is especially suited for determining the relative position of two bodies and their relative orientation.
U.S. Pat. No. 5,367,315 discloses a cursor control scheme using IR frequency signals. Although this microprocessor controlled IR light based system avoids some of the disadvantages typified by the mouse or other classically inefficient peripheral components, control of the cursor movement is effected through movement of the computer user's eyes and head, which movement is sensed by a plurality of light sensors positioned around the screen. In order to implement such a scheme, an array of transmitters are required along with an array of receivers around the display screen and this requires additional filtering to remove noise of the detected IR signal from the surrounding light reflections. This scheme is quite complicated and further requires multiplexing. Also, this scheme must consider not only movement of the head but also movement of both eyes of the computer user. Consequently, the algorithm associated therewith becomes quite cumbersome.
W 92/09983, published Jun. 11, 1992, is directed to the tracking and displaying of a virtual object using a radio frequency signal. The displayed virtual object mimics a transmitter which is a glove assembly supporting a transmitting device which transmits cursor data related to gesture information at a radio frequency to four stationary receivers around the display. The received RF signal is converted to a digital signal and is processed by a microprocessor. The software employed is such that the position of the virtual object is calculated based on the strength of the signal received and that the movement of the virtual object shown on the display is in the same direction as and is proportional to the object movement. With regard to this, an averaging method is employed to determine the object position. RF signals are effected by distance and, therefore, the tracking scheme employed is dependent on distance between the display and the glove assembly. Also, movement on the screen is proportional to movement of the glove assembly. Said differently, this RF tracking scheme tracks the location of the glove assembly and cannot be considered in the same sense as that of a direct pointer scheme which locates the X-Y coordinates of the target position the pointer is aimed at on the screen.